The present invention relates to a watertight brushless fan motor whose stator side is molded with an insulating material.
In a conventional watertight brushless fan motor disclosed in Japanese Laid-Open No. 10-191611, a stator in a stator side case and a groove in a web for receiving a lead wire are molded with a silicone rubber to make the stator side have a watertight structure. Even the conventional watertight brushless fan motor does not encounter any problem when it is used for a usual use.
However, if the conventional watertight brushless fan motor is used for a long time in the environmental conditions in which water containing oil mist is splashed on the fan motor, it is found that the fan motor encounters problems that the insulating ability of the molded part is deteriorated and that a rotor is hard to rotate.
It is an object of the present invention to provide a watertight brushless fan motor which can be used for a long time in the environmental conditions in which water containing oil mist is splashed on the fan motor.
It is another object of the present invention to provide a brushless fan motor which has a higher watertight effect than a conventional watertight brushless fan motor.
It is still another object of the present invention to provide a brushless fan motor which can prevent water from entering the inside of an iron core from a pole face.
The present invention is a watertight brushless fan motor comprising:
a stator provided with a plurality of stator magnetic poles, each of which has a winding wound around a projecting pole of an iron core constituted by a plurality of laminated steel plates;
a circuit substrate mounted with an electronic part constituting a control circuit for controlling a current flow through the winding, the circuit substrate being fixed to the stator;
a rotor having a plurality of rotor magnetic poles, each of which is made of a permanent magnet, on the inner peripheral side and having a plurality of blades on the outer peripheral side; and
a stator side case having a bearing supporting cylindrical section in which a bearing for rotatably supporting the rotary shaft of the rotor is received, a housing section for surrounding the outer periphery of the blades of the rotor, a substrate receiving section in which the circuit substrate is received, and a plurality of webs for connecting the substrate receiving section to the housing section, wherein a lead wire receiving groove for receiving a plurality of lead wires extending from the control circuit of the circuit substrate and for guiding them to the housing side is formed in one of the webs, wherein a communicating passage is formed between the lead wire receiving groove and the substrate receiving section, and wherein the stator, the circuit substrate including the electronic parts and the plurality of lead wires received in the lead wire receiving groove are molded with an electrically insulating material to form a molded part.
The present invention is characterized in that the stator, the circuit substrate including the electronic parts and the plurality of lead wires are molded with an epoxy resin having a Shore hardness of D30 to D90 after curing. The epoxy resin is resistant to oil mist and is neither swelled nor deteriorated in an insulating ability even if it is exposed to water containing oil mist for a longtime. Accordingly, this prevents the possibility that the gap between the rotor and the stator is reduced by the swelling of the molded part and that the rotation of the rotor is reduced. However, in reality, the epoxy resin is not used for forming the molded part embedding or molding the stator of the brushless fan motor. This is because it is thought that since the circuit substrate mounted with the electronic parts is positioned at the stator side, the electronic parts and the circuit substrate can not be protected from the stress generated in the insulating material which is cured to form the molded part. Also, this is because it is thought to be difficult to reduce the thickness of the molded part covering the pole faces of the stator core when the gap between the rotor and the stator is reduced to improve performance. As a result of various researches, the inventor has found that if the molded part is formed by an epoxy resin having a Shore hardness of D30 to D90 after curing, the molding accuracy and the mechanical strength of the molded part can be kept good and the stress applied to the electronic parts and the circuit substrate arranged in the molded part can be reduced and has completed the present invention.
Also, if water containing oil mist enters the bearing of the watertight brushless fan motor, it flows the grease in the bearing to greatly reduce the life of the bearing. Accordingly, in the present invention, in the case where the bearing supporting cylindrical section is shaped like a cylinder which is open at both ends, a bush fixed to the rotary shaft to fix the rotor side case to the rotary shaft and one open end portion of the bearing supporting cylindrical section are opposed to each other with a small gap between them to form a labyrinth structure for preventing water from entering the inside of the bearing. The other open end portion of the bearing supporting cylindrical section is hermetically sealed by a sealing member. If such a structure is adopted, it is possible to effectively prevent the water containing oil mist from entering the inside of the bearing and to greatly elongate the life of the bearing.
In the case where the gap between the rotor and the stator is reduced, it is difficult to keep the gap within a predetermined range even if the molding accuracy is increased. Accordingly, in this case, the molded part is made of the epoxy resin such that the pole faces of the plurality of projecting pole portions are exposed, and an insulating resin (for example, epoxy varnish) having the viscosity capable of making the insulating resin enter the inside of the iron core is applied to the pole faces of the plurality of projecting pole portions. This can reduce the gap between the pole face of the stator and the rotor and can effectively prevent the inside of the iron core from being impregnated by the water containing oil mist.